From the product profile for “HICOM 300 ‘Voice Mail Service VMS’: Siemens AG, 1995, Order No.: A31002-S10-A1-7-5”, a ‘Voice Mail Service VMS’ voice storage system is known which is integrated into a private ISDN switching system. Said voice storage system serves to store, retrieve, and distribute messages in natural-speech form. Users enrolled in the voice storage system have for this purpose been assigned a personal mailbox (“voice mailbox”). When absent, mailbox owners can divert calls intended for them to their mailbox, in which the messages conveyed with the calls are stored.
The enrolled users are able, by dialing their mailbox, to listen to their stored messages at any time and anywhere. Acoustic user prompting makes it easier to work with the voice storage system. Said system is operated with the aid of, for instance, frequency tones that conform to the dual-tone multifrequency (DTMF) signaling system and can be activated via a terminal's keypad.
After being listened to, a stored message can be deleted, stored, or further processed. For example a question asked by a subscriber who has left a voice message can be answered directly in that subscriber's mailbox. When a message has been listened to, a communication connection can also be set up directly to said subscriber without having to enter that person's directory number (callback).
The number of messages requiring to be stored briefly (for example during a meeting) or over the medium term (for example during several days' absence) is growing as a result of the increased use of voice storage systems (‘Voice Mail’). It is therefore in the mailbox owner's interest to deal with the totality of stored voice messages as promptly and simply as possible.
In the event of an unsuccessful callback attempt, which is to say a failure to set up a connection between the mailbox owner and a subscriber who has left a voice message, many voice storage systems allow users to leave a voice message and/or then without interruption continue with the processing of a next or, as the case may be, another voice message in terms of a logical ‘Voice Mail User Session’. If, conversely, an attempt to establish a connection to a subscriber who has left a voice message is successful, which is to say a desired two-way connection has been set up between the mailbox owner and subscriber with no further involvement of the voice storage system, then on termination of said two-way connection the connection to the voice storage system will also always be terminated.
After a successful connection between the mailbox owner and the subscriber who has left a voice message, in order to resume message processing the mailbox owner must set up another connection to the voice storage system to continue his/her ‘Voice Mail User Session’ with the next, or, as the case may be, another stored message, or with deleting the message just successfully processed. That means that all the necessary identification data and, where applicable, passwords will also have to be entered again while another connection is being set up.
A method is known from German patent specification DE 197 20 597 C2 that eliminates the need to re-enter the necessary identification data and, where applicable, passwords. For this purpose a second connection is established between a telecommunication system assigned to the mailbox owner and the message storage system before a first connection between the mailbox owner and the message storage system is replaced, with the directory number of the mailbox owner's terminal and that of the message storage system being stored in the telecommunication system. If the connection between the mailbox owner and subscriber is terminated at the subscriber's instigation, a first connection will then be re-established between the mailbox owner and message storage system using the directory numbers stored in the telecommunication system.
That, though, requires an additional interface, for example a CTI interface, between the telecommunication system and message storage system, which is associated with increased technical requirements.